boosting synctest & gosimnet, a channels-only network-mock

[Jason E. Aten]

Somehow I missed it when it was first announced, so only

recently did I discover the exciting testing/synctest experiment 

available in go1.24.

If you are a fan of repeatable, deterministic tests

for tricky concurrent code... you should really check 

out synctest.

My RPC package tests go 10x faster with the fake time

of synctest in place. Niiice.

Here is the post in case you missed it the first time

around like I did. https://go.dev/blog/synctest

And the docs, https://pkg.go.dev/testing/synctest

Caveats: one limitation of synctest is that it is kind of tricky to test network

code with it, because you aren't allowed to

talk to a "real" network. OS calls create

non-determinism. So you need a mocked or simulated

network, entirely in memory, using only channels,

for example.

I happened to need a network simulator myself for

testing my Raft implementation under partitions,

server power failures, reboots, etc... You know,

the general chaos that fault tolerant algorithms are

made for. Lacking a better alternative, I wrote one. 

If you dismissed synctest before because you didn't have a network

simulator... happy birthday. Gosimnet implements net.Conn

and can crash, reboot, and partition servers.

It's probably got bugs, I'd consider it alpha quality,

but those can be fixed.

https://github.com/glycerine/gosimnet

Enjoy.

Jason

[Jason E. Aten]

(If anyone more clever with hand illustration (or image gen AI...stable diffusion?) 

than me can contribute a better image of the Go Gopher playing with traffic, 

that would be great. While I still find it amusing, the current AI 

generated gopher is... not really satisfactory).